Aspergillus fumigatus is the leading airborne fungal pathogen in immune compromised people. Due to difficulties in managing A. fumigatus infections, most individuals that develop invasive aspergillosis will die. With an increasing immune compromised population, infections by A. fumigatus will also increase. While significant advancements in understanding aspergillosis have been made, the relationship among corresponding immune cells is not fully understood. The long-term goal of this work is to identify the molecular basis of host defense against A. fumigatus. The specific focus is to determine the cellular and molecular contact between phagocytes and A. fumigatus and the role of microbicidal responses in the corresponding immunity. Three aims are proposed to address this goal: 1) To evaluate the cell specific response to A. fumigatus conidia in the lungs of mice by flow cytometry and immunohistochemistry: Lung tissue will be probed using specific monoclonal antibodies to identify cells that arrive following inoculation of A. fumigatus conidia in normal and immune suppressed mice. Both cortisone-induced immune suppression and mice made susceptible to by knockout of the NADPH oxidase will be examined. 2) To investigate the role of the NADPH oxidase in subcellular compartments of immune cells which have ingested conidia: Superoxide generation assays will be used to show assembly of the oxidase associated with phagolysosomes containing ingested conidia. The assembled complex will be confirmed by demonstrating superoxide generation rates in compartments containing conidia, as well as demonstrating the complete set of oxidase components by immunoblot. A panel of monoclonal antibodies is available for oxidase detection. 3) To identify unique peptides that bind specifically to the A. fumigatus conidia and hyphal forms by phage-display peptide library analysis. Affinity selection of unique peptides will be carried out by probing the A. fumigatus resting conidia, swollen conidia, and hyphae with a peptide library. This information will be used to suggest mechanisms of attachment in this host-pathogen relationship [unreadable] [unreadable] [unreadable]